0.4.3a commit

+ added Fast Square Root to SmallBasic.cs
+ added method to calculate sum of numbers 0 to n (SumOfZtoN)
~ Encryption methods now use PBKDF2 to derive a key+vector of required length
- PBKDF2 method removed from SmallBasic.cs
- PasswordCrackTime method removed from SmallBasic.cs
- ESLCompute class removed